The objective of this research is to study the structure of bacteriophage T4 gene 32 product, a helix destabilizing protein, and examine its roles in DNA replication recombination and repair. The specific aim of this proposal is to elucidate interactions of 32 protein with itself and those with other proteins and understand how such interactions control and coordinate the activities of individual enzymes as well as the overall structure and activities of the replication-recombination complex. During the past granting periods, we started a line of research using limited proteolysis products of 32 protein to correlate the structure and functions of the protein. The results indicated that 32 protein has several descrete domains and some of the domains seemed to be specifically involved in protein-protein interactions. We plan to continue the same line of research with expansion to include mutationally and chemically modified protein research with intensified structure studies. Proposed experiments consist of preparation of various 32 protein fragments and mutationally or chemically modified proteins; chemical and physical studies to examine their structure and that of their macromolecular complexes; extensive use of 32 protein affinity chromatography to examine protein-protein and protein-DNA interactions as well as identification of 32-binding proteins; mapping of the contact area and detection of conformational changes by differential chemical modification; and use of 32 protein fragments and modified proteins in in vitro replication reactions to correlate the physical interactions with the functional ones.